Protection against the UV-radiation is an increasing issue in Denmark as the prognosis shows that the intensity of the radiation and the number of skin cancer patients will escalate in line with the dilution of the ozone layer. Over a period of 25 years incidents of skin cancer will grow with 20%. Skin cancer is just one out of many adverse effect of the UV-radiation. The problem with absent protection against the UV-radiation is not only a national concern but a global problem, e.g. in New Zealand where incidences of skin cancer are expected to increase by 50% within the next 10 years.
Ozone (or trioxygen, (O3)) is a triatomic molecule, consisting of three oxygen atoms. It is an allotrope of oxygen that is much less stable than the diatomic O2. Ground-level ozone is an air pollutant with harmful effects on the respiratory systems of animals. The ozone layer in the upper atmosphere filters potentially damaging ultraviolet light from reaching the Earth's surface.
The ozone molecules absorb ultraviolet radiation having wavelengths between 240 and 320 nm. The triatomic ozone molecule becomes diatomic molecular oxygen plus a free oxygen atom:O3(gas)+(240 nm<radiation<320 nm)→O2(gas)+O.(gas)
The atomic oxygen produced immediately reacts with other oxygen molecules to reform ozone:O2+O.+M→O3+Mwhere “M” denotes the third body that carries off the excess energy of the reaction. In this way, the chemical energy released when 0 and O2 combine is converted into kinetic energy of molecular motion. The overall effect is to convert penetrating UV light into heat, without any net loss of ozone. This cycle keeps the ozone layer in a stable balance while protecting the lower atmosphere from UV radiation, which is harmful to most living beings. It is also one of two major sources of heat in the stratosphere (the other being the kinetic energy released when O2 is photolyzed into O atoms).
Curl, Kroto and Smalley (Kroto, et al. Nature, Vol 318, p. 162, 1985) were the first to make and identify C60-fullerenes (“buckyballs”) in the laboratory. One of the most common routes towards the native fullerenes involves the heating of graphite rods to a high temperature by passing an electric current between them, and then separating the fullerenes from other carbon compounds in the resulting soot (fine carbon particles). Typically, about 75% of the crystals are C60-fullerene molecules, 23% are C70-fullerene molecules and the remains comprise larger molecules. Later on, various other groups have been able to prepare larger quantities of fullerenes, also on a commercial scale, and nowadays C60-, C70-, C76-, C78-, C82- and C84-fullerenes and a variety of derivatives are available from commercial sources, just as the production price has been dramatically reduced. Birkett has prepared an excellent review of the chemistry of fullerenes (http://www.rsc.org/ej/IC/1998/ic094055.pdf).
General methods and consideration for the preparation of fullerenes are described in Karl M. Kadish & Rodney S. Ruoff, “Fullerenes—Chemistry, Physics, and Technology”, Wiley-Interscience 2000, ISBN 0-471-29089-0. Chapter 8: Endohedral Metallofullerenes Production, Separation, and Structural Properties.